scholarly journals Numerical Study of Simultaneous Multiple Fracture Propagation in Changning Shale Gas Field

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1335 ◽  
Author(s):  
Jun Xie ◽  
Haoyong Huang ◽  
Yu Sang ◽  
Yu Fan ◽  
Juan Chen ◽  
...  
Keyword(s):  
Shale Gas ◽  
Fracture Propagation ◽  
Injection Rate ◽  
Propagation Model ◽  
Fluid Viscosity ◽  
Multiple Fracture ◽  
Gas Field ◽  
Fracture Spacing ◽  
Stress Shadow ◽  
Engineering Parameters

Recently, the Changning shale gas field has been one of the most outstanding shale plays in China for unconventional gas exploitation. Based on the more practical experience of hydraulic fracturing, the economic gas production from this field can be optimized and gradually improved. However, further optimization of the fracture design requires a deeper understanding of the effects of engineering parameters on simultaneous multiple fracture propagation. It can increase the effective fracture number and the well performance. In this paper, based on the Changning field data, a complex fracture propagation model was established. A series of case studies were investigated to analyze the effects of engineering parameters on simultaneous multiple fracture propagation. The fracture spacing, perforating number, injection rate, fluid viscosity and number of fractures within one stage were considered. The simulation results show that smaller fracture spacing implies stronger stress shadow effects, which significantly reduces the perforating efficiency. The perforating number is a critical parameter that has a big impact on the cluster efficiency. In addition, one cluster with a smaller perforating number can more easily generate a uniform fracture geometry. A higher injection rate is better for promoting uniform fluid volume distribution, with each cluster growing more evenly. An increasing fluid viscosity increases the variation of fluid distribution between perforation clusters, resulting in the increasing gap between the interior fracture and outer fractures. An increasing number of fractures within the stage increases the stress shadow among fractures, resulting in a larger total fracture length and a smaller average fracture width. This work provides key guidelines for improving the effectiveness of hydraulic fracture treatments.

scholarly journals Numerical Study of the Effect of Perforation Friction and Engineering Parameters on Multicluster Fracturing in Horizontal Wells

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Zixi Jiao ◽  
Anlin Zhang ◽  
Longhuan Du ◽  
Yang Yang ◽  
Hua Fan
Keyword(s):  
Flow Rate ◽  
Propagation Model ◽  
Fluid Viscosity ◽  
Multiple Fracture ◽  
Multiple Fractures ◽  
Shadow Effect ◽  
Stress Shadow ◽  
Dynamic Partitioning ◽  
Initiation And Propagation ◽  
Engineering Parameters

Simultaneous multiple-fracture treatments in horizontal wellbores have become one of the key methods for economically and efficiently developing oil and gas resources in unconventional reservoirs. However, field data show that some perforation clusters have difficulty propagating fractures due to the internal mechanism of competing initiation and propagation among the fractures. In this paper, the physical mechanisms that influence simultaneous multiple-fracture initiation and propagation are investigated, and the effects of engineering parameters and in situ conditions on the nonuniform development of multiple fractures are discussed. A 3D fracture propagation model was established with ABAQUS to show the influence of the stress shadow effects and dynamic partitioning of the flow rate by simulating the propagation of multiple competing fractures generated in the perforation clusters. Based on the results of these simulations, simultaneous flow in multiple fractures can propagate evenly. Through adjusting the number of perforations in each cluster or the perforation diameter, the effect of the stress shadow can be significantly reduced by increasing the perforation friction, and the factors that affect the development of multiple fractures are changed, from the stress shadow effect to the dynamic partitioning of the flow rate. When the stress shadow effect is dominant, increasing the fracturing fluid viscosity promotes the uniform development of multiple fractures and increases the fracture width. When the dynamic partitioning of the flow rate is dominant, increasing the injection rate greatly affects the uniform development of multiple fractures.

scholarly journals Factors affecting reorientation of hydraulically induced fracture during fracturing with oriented perforations in shale gas reservoirs

2021 ◽  
Vol 15 (58) ◽  
pp. 1-20
Author(s):  
Qingchao Li ◽  
Liang Zhou ◽  
Zhi-Min Li ◽  
Zhen-Hua Liu ◽  
Yong Fang ◽  
...  
Keyword(s):  
Shale Gas ◽  
Injection Rate ◽  
Single Fracture ◽  
Fluid Viscosity ◽  
Fracture Conductivity ◽  
Factors Affecting ◽  
Controllable Factors ◽  
Initiation Pressure ◽  
Shale Reservoirs ◽  
Induced Fractures

Hydraulic fracturing with oriented perforations is an effective technology for reservoir stimulation for gas development in shale reservoirs. However, fracture reorientation during fracturing operation can affect the fracture conductivity and hinder the effective production of shale gas. In the present work, a numerical simulation model for investigating fracture reorientation during fracturing with oriented perforations was established, and it was verified to be suitable for all investigations in this paper. Based on this, factors (such as injection rate and fluid viscosity) affecting both of initiation and reorientation of the hydraulically induced fractures were investigated. The investigation results show that the fluid viscosity has little effect on initiation pressure of hydraulically induced fracture during fracturing operation, and the initiation pressure is mainly affected by perforation azimuth, injection rate and the stress difference. Moreover, the investigation results also show that perforation azimuth and difference between two horizontal principle stresses are the two most important factors affecting fracture reorientation. Based on the investigation results, the optimization of fracturing design can be achieved by adjusting some controllable factors. However, the regret is that the research object herein is a single fracture, and the interaction between fractures during fracturing operation needs to be further explored.

scholarly journals Analysis of Hydraulic Fracture Propagation Using a Mixed Mode and a Uniaxial Strain Model considering Geomechanical Properties in a Naturally Fractured Shale Reservoir

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Youngho Jang ◽  
Gayoung Park ◽  
Seoyoon Kwon ◽  
Baehyun Min
Keyword(s):  
Shale Gas ◽  
Hydraulic Fracture ◽  
Mixed Mode ◽  
Fracture Propagation ◽  
Fracture Network ◽  
Uniaxial Strain ◽  
Propagation Model ◽  
Geomechanical Properties ◽  
Hydraulic Fracture Propagation ◽  
Strain Model

This study proposes a hydraulic fracture propagation model with a mixed mode comprising opening and sliding modes to describe a complex fracture network in a naturally fractured shale gas formation. We combine the fracture propagation model with the mixed mode and the uniaxial strain model with tectonic impacts to calculate the stress distribution using geomechanical properties. A discrete fracture network is employed to realize the fracture network composed of natural and hydraulic fractures. We compare the fracture propagation behaviours of three cases representing the Barnett, Marcellus, and Eagle Ford shale gas formations. Sensitivity analysis is performed to investigate the effects of the geomechanical properties of the reservoir on the sliding mode’s contribution to the mixed mode. The numerical results highlight the significance of the mixed mode for the accurate assessment of fracture propagation behaviours in shale gas formations with high brittleness.

Mechanisms of Simultaneous Hydraulic-Fracture Propagation From Multiple Perforation Clusters in Horizontal Wells

SPE Journal ◽  
2016 ◽  
Vol 21 (03) ◽  
pp. 1000-1008 ◽  
Author(s):  
Kan Wu ◽  
Jon E. Olson
Keyword(s):  
Flow Rate ◽  
Flow Resistance ◽  
Fracture Propagation ◽  
Propagation Model ◽  
Additional Stress ◽  
Hydraulic Fractures ◽  
Multiple Fracture ◽  
Negative Effects ◽  
Multiple Fractures ◽  
Effects Of Stress

Summary Simultaneous multiple-fracture treatments in horizontal wellbores are becoming a prevalent approach to economically develop unconventional resources in shale reservoirs. One challenge to efficiently use the technique is the generation of effective hydraulic fractures from all perforation clusters. In this work, we conducted a fundamental study of physical mechanisms controlling simultaneous multiple-fracture propagation and discussed the potential approaches to improve nonuniform development of multiple fractures. This study was investigated by our recently developed 3D fracture-propagation model that captures the coupled elastic deformation of the rock with fluid flow in the horizontal wellbore and within the fractures. The model demonstrated that fracture geometry was controlled by both the stress-shadow effects and dynamic partitioning of flow rate. The analysis results indicated that the nonuniform development of a multiple-fracture array, for example, a three-fracture array in this study, was induced by the uneven partitioning of flow rate into each fracture, which was dependent on the flow resistance from wellbore friction, perforation friction, and fracture propagation. Furthermore, the stress shadowing from the exterior fractures exerted additional stress on the interior fractures and increased the resistance of fracture propagation, resulting in the interior fractures receiving much less fluid. To minimize the negative effects of stress shadowing and favor more-uniform fracture growth, we investigated potential approaches to promote uniform partitioning of flow rate through adjusting the flow resistance between multiple fractures. The results showed that adjusting perforation friction can provide an effective way to modify the partitioning of flow rate and mitigate the negative effects of stress shadowing. The mechanisms investigated in this study are consistent with field observations. Our approach can help field operators to improve the effectiveness of multiple fracturing treatments and maximize the production.

scholarly journals Numerical Investigation of Hydraulic Fracture Propagation in Naturally Fractured Reservoirs Based on Lattice Spring Model

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Kaikai Zhao ◽  
Pengfei Jiang ◽  
Yanjun Feng ◽  
Xiaodong Sun ◽  
Lixing Cheng ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Fractured Reservoirs ◽  
Fracture Propagation ◽  
Maximum Principal Stress ◽  
Injection Rate ◽  
Naturally Fractured Reservoirs ◽  
Fluid Viscosity ◽  
Global Orientation ◽  
Hf Propagation

Hydraulic fracturing has been extensively employed for permeability enhancement in low-permeability reservoirs. The geometry of the hydraulic fracture network (HFN) may have implications for the optimization of hydraulic fracturing operations. Various parameters, including the in situ stress, treatment parameters (injection rate and fluid viscosity), and orientation of natural fractures (NFs), can significantly affect the interactions between hydraulic fracture (HF) and NFs and the final HFN. In this study, a lattice-spring code was employed to determine the impact of various parameters on the geometry of the HFN. The modelling results indicated that with a large stress difference, the global orientation of the fracture propagation was restricted to the direction of maximum principal stress, and the number of fracture branches was reduced. The geometry of the HFN changed from circular to elliptical. In contrast, with an increase in the fluid viscosity/injection rate, the evolution of the geometry of the HFN exhibited the opposite trend. The global orientation of HF propagation tended to remain parallel to the direction of maximum principal stress, regardless of the branching and tortuosity of the fracture. The variations in the ratio of tensile fracture (HF) to shear fracture (shear slip on NF) can be significant, depending on the stress state, treatment parameters, and preexisting NF network, which determine the dominant stimulation mechanism. This study provides insight into the HF propagation in naturally fractured reservoirs.

scholarly journals Numerical Investigation of Hydraulic Fracture Extension Based on the Meshless Method

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Chaoneng Zhao ◽  
Yongquan Hu ◽  
Jinzhou Zhao ◽  
Qiang Wang ◽  
Pei He ◽  
...  
Keyword(s):  
Hydraulic Fracture ◽  
Fracture Propagation ◽  
Propagation Model ◽  
Propagation Path ◽  
Hydraulic Fractures ◽  
Stress Inversion ◽  
Stress Shadow ◽  
Single Well ◽  
Hydraulic Fracture Propagation ◽  
Element Free

The fracture propagation in hydraulic fracturing is described as a nonlinear problem dynamic boundary. Due to the limitation of mesh refinement, it is difficult to obtain the real crack propagation path using conventional numerical methods. Meshless methods (MMs) are an effective method to eliminate the dependence on the computational grid in the simulation of fracture propagation. In this paper, a hydraulic fracture propagation model is established based on the element-free Galerkin (EFG) method by introducing jump and branch enrichment functions. Based on the proposed method, three types of fracturing technology are investigated. The results reveal that the stress interference between fractures has an important impact on the propagation path. For the codirectional fracturing simultaneously, fractures propagate in a repel direction. However, the new fracture is attracted and eventually trapped by the adjacent fracture in the sequential fracturing case. For the opposite simultaneous fracturing in multiwells, two fractures with a certain lateral spacing will deflect toward each other. The effect of stress shadow should be used rationally in the optimization of construction parameters; for the single well multistage fracturing, the stage spacing should be out of stress inversion area, while for the simultaneous fracturing of multiple wells, stress inversion zones should be used to maximize communication between natural fractures. Overall, this study establishes a novel and effective approach of using MM to simulate the propagation of hydraulic fractures, which can serve as a useful reference for understanding the mechanism of hydraulic fracture propagation under various conditions.

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